1. Field of the Invention
The present invention relates to a control apparatus for a vehicle having an idling stop function and a vehicle stop maintaining function.
2. Description of Related Art
An idling stop technology in which an engine is stopped while a vehicle is stopped by a driver's operation on a brake pedal is known. Also, a technology in which the engine that has been stopped by the idling stop technology is restarted when the driver's foot is moved away from the brake pedal is known. The both technologies are collectively called idling stop function, start & stop function, engine-automatically-start-stop function, or the like (hereinafter, simply referred to as “idling stop function”).
In addition, there is also a technology in which the braked state of the vehicle is maintained even though the driver has moved his foot away from the brake pedal while the vehicle is being stopped, which technology is referred to as braking maintenance function and/or hill-start assistance (hereinafter, simply referred to as “vehicle stop maintaining function”), or the like. With this technology, when the vehicle is stopped before a traffic light, the driver does not need to depress the brake pedal, so the driver's fatigue may be alleviated.
In a vehicle in which the idling stop function and the vehicle stop maintaining function are both operatable, after the engine is stopped by the idling stop function, the driver brings the vehicle stop maintaining function into operation, thus even if the driver moves his foot away from the brake pedal, the idling stop function would not be activated, and the engine will not be restarted. Thus, an OFF state of the brake pedal is excluded from the engine start conditions, and the engine will be restarted by an ON operation on an accelerator pedal.
In addition, the braking force by the vehicle stop maintaining function is generated by increasing the hydraulic pressure of wheel cylinders by means of a pump hydraulic pressure, and thus, when this function is in operation for a long time, there may occur a problem that a remaining capacity of a battery decreases. Thus, there is a technology in which the braking of the vehicle provided by using hydraulic pressure is switched to the braking of the vehicle provided by EPB (Electronic Parking Brake) in the case where the vehicle stop maintaining function has been in operation for a predetermined time, so as to avoid the vehicle stop maintaining function from being in operation for a long time (for example, refer to Japanese Patent Application Publication No. 2012-11969 (JP 2012-11969 A)).
However, with the braking force being provided by the parking brake, the vehicle may be moved when the engine is started by the idling stop function.
FIG. 1 is an exemplary diagram for illustrating the variation of the braking force with time. Since a predetermined time lapses while the vehicle stop maintaining function is in operation, at time t1, the vehicle stop maintaining function stops the braking provided by the hydraulic pressure, and starts the braking provided by the EPB. At time t1, the braking force provided by the EPB is increased, and the braking force provided by the hydraulic pressure is gradually decreased since time t1.
Therefore, for example, like at time t2 at which a long time has lapsed since the shifting into the EPB, the vehicle is stopped only by the braking force provided by the EPB. If the engine is started by the idling stop function in this state, according to the braking force of the EPB, the vehicle is likely to be moved by a driving force incurred by the speed-up of the engine and/or by a creeping after start.
In addition, the vehicle stop maintaining function releases the EP3 through an ON operation on the accelerator pedal, and the idling stop function starts the engine through an ON operation on the accelerator pedal. However, because the control on the braking force of the EPB has a slower responsiveness than the control on the braking force provided by the hydraulic pressure, the starting response may be degraded when the release of the EPB and the start of the engine are carried out simultaneously.